The R Project SVN R

///////////////////////////////////////////////////////////////////////////////
//
/// \file       vli_encoder.c
/// \brief      Encodes variable-length integers
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "common.h"


extern LZMA_API(lzma_ret)
lzma_vli_encode(lzma_vli vli, size_t *vli_pos,
        uint8_t *restrict out, size_t *restrict out_pos,
        size_t out_size)
{
    // If we haven't been given vli_pos, work in single-call mode.
    size_t vli_pos_internal = 0;
    if (vli_pos == NULL) {
        vli_pos = &vli_pos_internal;

        // In single-call mode, we expect that the caller has
        // reserved enough output space.
        if (*out_pos >= out_size)
            return LZMA_PROG_ERROR;
    } else {
        // This never happens when we are called by liblzma, but
        // may happen if called directly from an application.
        if (*out_pos >= out_size)
            return LZMA_BUF_ERROR;
    }

    // Validate the arguments.
    if (*vli_pos >= LZMA_VLI_BYTES_MAX || vli > LZMA_VLI_MAX)
        return LZMA_PROG_ERROR;

    // Shift vli so that the next bits to encode are the lowest. In
    // single-call mode this never changes vli since *vli_pos is zero.
    vli >>= *vli_pos * 7;

    // Write the non-last bytes in a loop.
    while (vli >= 0x80) {
        // We don't need *vli_pos during this function call anymore,
        // but update it here so that it is ready if we need to
        // return before the whole integer has been decoded.
        ++*vli_pos;
        assert(*vli_pos < LZMA_VLI_BYTES_MAX);

        // Write the next byte.
        out[*out_pos] = (uint8_t)(vli) | 0x80;
        vli >>= 7;

        if (++*out_pos == out_size)
            return vli_pos == &vli_pos_internal
                    ? LZMA_PROG_ERROR : LZMA_OK;
    }

    // Write the last byte.
    out[*out_pos] = (uint8_t)(vli);
    ++*out_pos;
    ++*vli_pos;

    return vli_pos == &vli_pos_internal ? LZMA_OK : LZMA_STREAM_END;

}